I believe the answer is tertiary
<span>for accurate results, for example when they are making vaccines, these are weakened harmful or disease causing viruses,, too little of the virus then it would not be a vaccine or simply would not build you antibodies, and too much of it would not also not a vaccine since it will already inflict a disease or possibly be fatal</span>
There's a group on each side so there's equal pull on both sides so it doesn't move
